Nuclear mitotic apparatus protein (NuMA) is a large 236 KDa coiled-coil protein with a globular head and tail, and is a predominantly nuclear protein that is present in the interphase nucleus and is concentrated in the spindle pole of mitotic cells. NuMA is also known as centrophilin, SPN, SP-H, 1H1/1F1, and W1 (Tang et al. “Nuclear mitotic apparatus protein (NuMA): spindle association, nuclear targeting and differential subcellular localization of various NuMA isoforms.” Journal of Cell Science 107: 1389-1402 (1994)). NuMA converges on microtubules at the minus ends, a function that is essential for spindle organization. In dividing cells, upon phosphorylation, NuMA disperses into the cytoplasm, associates with cytoplasmic dynein/dynactin to form a complex, and translocates along microtubules to the spindle poles where it organizes and tethers microtubules to spindle poles. NuMA becomes dephosphorylated, loses its association with dynein/dynactin, and releases from spindle poles after anaphase onset to allow spindle disassembly and reformation of interphase daughter nuclei. The cell-cycle-dependent phosphorylation of NuMA is regulated by the balanced activities of protein kinases and phosphatases. It has been shown that phosphorylation of NuMA by cyclin B/cdc2 kinase allows NuMA to release from the nucleus and to associate with centrosomes and/or microtubules at the spindle poles, while NuMA's dephosphorylation due to the cyclin B degradation allows NuMA to dissociate from the spindle poles after anaphase onset. Overexpression of NuMA interferes with spindle-associated dynein localization and promotes multipolar spindle formation and cancer. On the other hand, NuMA is absent in many kinds of non-proliferating cells and highly differentiated cells. NuMA also functions during meiotic spindle organization in male and female germ cells. Degradation of NuMA results in the breakdown of normal nuclear structure, and has been used as a marker of cell apoptosis.
Any discrepancy in the function of NuMA leads to disruption of microtubule focusing at spindle poles leading to splaying of microtubule ends. NuMA resides in the nucleus during interphase and becomes transiently associated with mitotic centrosomes after multiple steps of phosphorylations. NuMA responds to external signals such as hormones that induce cell divisions or heat shock that induce apoptosis. At prophase NuMA disperses in the cytoplasm and associates with microtubules. During meta- or anaphase NuMA gets associated with chromatin and finally to the reconstituted nucleus. NuMA is a cell cycle-related protein essential for normal mitosis that gets degraded in early apoptosis. NuMA forms a complex with cytoplasmic dynein and dynactin. The depletion of the complex lead to failure in normal assembly of mitotic spindles. NuMA gets PARsylated by tankyrase-1 during mitosis.
Studies conducted by Comptom and Cleveland (1993) have suggested that NuMA is required for the proper terminal phases of chromosome separation and/or nuclear reassembly during mitosis. Microinjection of anti-NuMA antibodies into early mitotic or metaphase cells was found by Yang et al. “An unusually long coiled-coil related protein in the mammalian nucleus.” J. Cell Biol. 116(6): 1303-1317 (1992), to prevent the formation or cause the collapse of the mitotic spindle apparatus, thus suggesting that NuMA may play an important role during mitosis.
Several studies have described a link between NuMA and cancer, but have not established that NuMA inhibition can treat cancer. NuMA is released from cells undergoing apoptosis (Miller et al., Biotechniques, 15:1042, 1993) and has been detected in the serum of patients with a wide range of cancers (Miller et al., Cancer Res., 52:422, 1992), and specifically in the urine of patients with bladder cancer (Stampfer et al., J. Urol., 159:394, 1998).
In WO/2005/014846, NuMA is regarded as a relevant target in methods for identifying risk of breast cancer in a subject and/or a subject at risk of breast cancer, reagents and kits for carrying out the methods, methods for identifying candidate therapeutics for treating breast cancer, and therapeutic methods for treating breast cancer in a subject. Variations in the NuMA gene were associated with familial breast cancer risk.
U.S. Pat. No. 6,287,790 describes a method for distinguishing malignant and proliferating non-malignant cells by cell immunostaining using a NuMA specific antibody, and microscopic analysis of NuMA distribution within each nucleus.
U.S. Pat. No. 6,864,238 describes polypeptides, and polynucleotides encoding such polypeptides, that are useful for destabilizing microtubules. Since microtubules play an essential role in cell division, which occurs more frequently in tumor cells, the polypeptides and polynucleotides can be useful in preparing a composition for inhibiting cell proliferation for treating a tumor.
US 20030125290 describes a composition comprising useful triethyleneglycol cholesteryl oligonucleotides for induction of response in a cell, including but not limited to inhibition of cellular proliferation, induction of cell cycle arrest, induction of caspase activation, cleavage of poly(ADP-ribose) polymerase, induction of apoptosis or modulation of extracellular matrix-cell interactions, or combinations thereof, in cancer cells or synovial cells, and methods of using this composition for treating disease. The release of NuMA was used as a measure of apoptosis.
WO9640917A describes methods and compositions for identifying proteins which interact non-covalently with NuMA in a cell, novel proteins identified by the method, and methods and compositions for interfering with this interaction in vivo.
El Bashir et al. “Duplexes of 21-nucleotide RNAs mediate RNA interference in cultured mammalian cells” Nature 411: 494-498 (2001), describes a 21 nucleotide siRNAs against NuMA downregulating NuMA protein expression in vitro.
Chang et al., “NuMA is a major acceptor of poly(ADP-ribosyl)ation by tankyrase 1 in mitosis” Biochem. J.: 391:117-184 (2005), describe the use of siRNA against NuMA to study NuMA function in human cells in vitro.